Engine valve actuation system and method using reduced pressure common rail and dedicated engine valve

ABSTRACT

A system and method for actuating an engine valve to provide engine braking and/or exhaust gas recirculation using a common source of hydraulic fluid is disclosed. The system receives high pressure hydraulic fluid from a common rail system, such as those used to provide fuel injection. The fluid pressure is reduced before being used to actuate an engine valve for engine braking or EGR. Preferably an engine valve that is dedicated to the engine braking or EGR function is provided in the engine. The dedicated engine braking/EGR valve may be driven by an electromagnetic actuator in an alternative embodiment.

FIELD OF THE INVENTION

[0001] The present invention relates to methods and apparatus foractuating an engine valve in an internal combustion engine to achieve acompression-release braking event, a bleeder type engine braking event,and/or an internal exhaust gas recirculation (EGR) event.

BACKGROUND OF THE INVENTION

[0002] During engine braking, the exhaust valves may be selectivelyopened to convert, at least temporarily, a power producing internalcombustion engine into a power absorbing air compressor. As a pistontravels upward during its compression stroke, the gases that are trappedin the cylinder are compressed. The compressed gases oppose the upwardmotion of the piston. During engine braking operation, as the pistonnears top dead center (TDC), at least one engine valve that communicateswith the exhaust manifold may be opened to release the compressed gases,preventing the energy stored in the compressed gases from being returnedto the engine on the subsequent expansion down-stroke. In doing so, theengine develops retarding power to help slow the vehicle down.

[0003] The operation of a compression-release type engine brake, asdescribed in the preceding paragraph has long been known. One of theearliest descriptions of a system used for compression-release brakingis provided in Cummins, U.S. Pat. No. 3,220,392. The system described inthe Cummins '392 patent derives the motion to open a pair of exhaustvalves for a compression-release event from an existing intake, exhaust,or injector pushrod or rocker arm. The compression-release motion isconveyed from a pushrod or rocker arm to a bridge joining two exhaustvalves by a selectively expandable hydraulic linkage. This hydrauliclinkage is expanded to convey the compression-release motion duringengine braking operation, and contracted to absorb such motion duringpositive power operation. The contraction of the hydraulic linkageduring positive power operation causes the compression-release motion tobe “lost” during positive power, and accordingly, such systems arecommonly referred to as “lost motion” valve actuation systems.

[0004] In the lost motion systems, such as the Cummins system, theengine valves are typically driven by fixed profile cams, morespecifically, by one or more fixed lobes on each of the cams. The use offixed profile cams makes it difficult to adjust the timing and/ormagnitude of the engine valve lift needed to optimize engine performancefor various engine operating conditions, such as different engine speedsduring engine braking.

[0005] Over the years there have been various improvements to thesystems and methods described in the Cummins '392 patent. One suchimprovement has been to use a common source of high pressure fluid, suchas that used for fuel injection systems, to actuate one or more valvesfor engine braking. Such systems are often called “common rail” systems.In common rail valve actuation systems, a source of high pressurehydraulic fluid is selectively applied to an actuator piston to actuateone or more valves for the compression-release events. The valves chosenfor actuation to achieve engine braking are most commonly exhaustvalves. Examples of such systems are shown in Sickler, U.S. Pat. No.4,572,114, Pitzi, U.S. Pat. No. 5,012,778, and Meistrick et al., U.S.Pat. Nos. 5,787,859, 5,809,964, and 6,082,328, each of which are herebyincorporated by reference. In some common rail systems, a dedicatedauxiliary valve is provided for engine braking. Examples of such systemsare shown in Korte et al., U.S. Pat. No. 5,564,386, Schmidt et al., U.S.Pat. No. 5,609,134, and Bergmann, U.S. Pat. No. 5,794,590, each of whichare hereby incorporated by reference.

[0006] Common rail systems may provide virtually limitless adjustment tovalve timing because the source of high pressure hydraulic fluid isconstantly available for valve actuation. Because common rail systemstheoretically may provide almost infinite variation in valve timing,they may be used to carry out almost any type of engine valve event,such as intake, exhaust, compression-release braking, bleeder braking,or exhaust gas recirculation (EGR), so long as the valve being actuatedhas communication with the appropriate manifold (i.e. the intake orexhaust manifold). Accordingly, given sophisticated and high speedcontrol over the application of this hydraulic pressure, a common railsystem should be able to deliver valve actuation on demand for a varietyof valve events, as well as provide some control over lift and duration.

[0007] To date, however, common rail engine valve actuation systems usedfor braking and EGR have not been widely used. The necessarysophisticated control, particularly in the seating of engine valves, hasnot been effectively realized. Two problems in particular that tend todiscourage the use of common rail actuation systems are the expense ofthe components required to exercise the level of control called for, andthe susceptibility of the system to complete failure in the event of aloss in hydraulic pressure. Until these problems are solved, it islikely that lost motion systems will continue to be the predominate typeof system used to carry out engine braking.

[0008] The foregoing problems with common rail systems stem in part fromthe use of very high pressure sources to open the engine valves, and inpart from the reliance on the systems to carry out critical valveevents, i.e. main intake and main exhaust events. The proposed use ofvery high pressure systems for common rail engine braking has resultedfrom the plan to piggy-back the engine braking system off of the commonrail fuel injection system that is already installed on a vehicle. This“piggy-backing” is thought to provide significant cost savings becauseonly one high pressure source (and set of components) may be needed fortwo systems, engine braking and fuel injection. Because fuel injectionrequires very high pressures, on the order of 3000 psi, attempts havebeen made to provide an engine braking common rail system that usesfluid at a similar pressure. Use of such high pressure, however,dictates the use of a very high force return spring for the actuatedvalve, which in turn requires complicated valve seating apparatus.Furthermore, leakage is more of a problem for high pressure systems, andcomponent design is inherently more critical and expensive. Accordingly,there is a need for a common rail system that may be used for enginebraking and EGR that does not suffer from the disadvantages thataccompany the use of high pressure fluid for common rail actuation.

[0009] A second significant challenge that arises from the use of commonrail systems for engine valve actuation is the potential for failure ofthe system. An hydraulic system suffers from vulnerability to failure asa result of fluid leakage. The greater the extent of leakage preventionmeasures, the more expensive the system becomes. Failure of a commonrail system to deliver engine braking and/or EGR would not in and ofitself be catastrophic since the vehicle could certainly be operatedwithout these features, albeit sub-optimally. Loss of main intake ormain exhaust valve events, however, cannot be tolerated because itresults in the complete failure of the engine. Accordingly, there is aneed for a common rail system that is responsible only for enginebraking and/or EGR valve events, but is not required for main intake ormain exhaust engine valve events.

[0010] Applicants have solved various of the foregoing challenges to theeffective use of common rail systems for engine braking and EGR bycoupling a reduced pressure common rail system, or anelectromagnetically driven actuator, with a dedicated engine braking/EGRengine valve. The use of reduced pressure reduces the likelihood andeffect of leakage, and reduces valve train load. Furthermore, such asystem may provide near infinite timing variations for engine brakingand internal EGR without jeopardizing the main intake and exhaust valveoperation.

[0011] Additional objects and advantages of some, but not necessarilyall, of embodiments of the present invention are set forth, in part, inthe description which follows and, in part, will be apparent to one ofordinary skill in the art from the description and/or from the practiceof the invention.

SUMMARY OF THE INVENTION

[0012] Responsive to the foregoing challenges, Applicants have developedan innovative engine valve actuation system for engine braking and/orexhaust gas recirculation comprising: a high pressure hydraulic fluidsource; a fluid pressure reduction device connected to the high pressurehydraulic fluid source; a hydraulic fluid control valve connected to thefluid pressure reduction device; and an engine valve actuator connectedto the hydraulic fluid control valve.

[0013] In one embodiment, the present invention is an engine valveactuation system comprising: a high pressure hydraulic fluid passage; ahigh pressure hydraulic fluid source; a fluid pressure reduction deviceconnected to the hydraulic fluid source through the high pressurehydraulic fluid passage; a low pressure hydraulic fluid passage; ahydraulic fluid control valve connected to the fluid pressure reductiondevice through the low pressure hydraulic fluid passage; an actuatorhydraulic fluid passage; and an engine valve actuator for producing anengine valve event, the engine valve actuator communicating with thehydraulic fluid control valve through the actuator hydraulic fluidpassage.

[0014] In another embodiment, the present invention is a method foractuating an engine valve in an internal combustion engine to produce anengine valve event. The method may comprise the steps of: providinghydraulic fluid to a fluid pressure reduction device; reducing thepressure of the hydraulic fluid from a first pressure to a secondpressure; selectively applying the hydraulic fluid at the secondpressure to an engine valve actuator; and actuating the engine valve toproduce the engine valve event.

[0015] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only, and are not restrictive of the invention as claimed.The accompanying drawings, which are incorporated herein by reference,and which constitute a part of this specification, illustrate certainembodiments of the invention and, together with the detaileddescription, serve to explain the principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to assist the understanding of this invention, referencewill now be made to the appended drawings, in which like referencecharacters refer to like elements. The drawings are exemplary only, andshould not be construed as limiting the invention.

[0017]FIG. 1 is a block diagram of an engine valve actuation systemaccording to a first embodiment of the present invention.

[0018]FIG. 2 is a block diagram of an engine valve actuation systemaccording to a second embodiment of the present invention.

[0019]FIG. 3 is a schematic diagram of an engine valve actuation systemaccording to a third embodiment of the present invention.

[0020]FIG. 4 is a block diagram of an engine valve actuation systemaccording to a fourth embodiment of the invention.

[0021]FIG. 5 is a schematic diagram of an engine valve actuation systemaccording to a fifth embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0022] Reference will now be made in detail to embodiments of thepresent invention, an example of which is illustrated in theaccompanying drawings. With reference to FIG. 1, a valve actuationsystem 10 for an internal combustion engine is shown. In one embodiment,the valve actuation system 10 may comprise: a high pressure hydraulicfluid source 100; a fluid pressure reduction device 300 connected to thehigh pressure hydraulic fluid source 100; a hydraulic fluid controlvalve 400 connected to the fluid pressure reduction device 300; and anengine valve actuator 600 connected to the hydraulic fluid control valve400 for actuating an engine valve 700. The engine valve 700 may comprisea dedicated braking valve. It is contemplated, however, that the enginevalve 700 may comprise an exhaust valve, and/or an intake valve.

[0023] In another embodiment of the present invention, as shown in FIG.2, the valve actuation system 10 may further comprise an accumulator 500connected to the hydraulic fluid control valve 400; and a low pressurehydraulic fluid tank 200 connected to the high pressure fluid source100.

[0024] With reference to FIG. 3, in one embodiment of the invention thevalve actuation system 10 includes a high pressure fluid source 100,such as may be used to supply a common rail fuel injection system. Thehydraulic electronic unit injection (HEUI) system sold by NavistarInternational is one example of such a common rail fuel injectionsystem.

[0025] The high pressure fluid source 100 may include a high pressurepump 110, a pressure regulator 120, and a high pressure plenum 130. Thehigh pressure fluid pump 110 may draw hydraulic fluid, such as dieselfuel, from a low pressure tank 200. The fluid pressure provided by pump110 may be on the order of several thousand (e.g. 3000) psi. Highpressure fluid sources 100 are known in the art for fuel injectionsystems. The pressure provided by the high pressure fluid source 100 maybe indicated by pressure P1.

[0026] In the embodiment of the present invention shown in FIG. 3, thehigh pressure fluid provided by the source 100 may be used, not only toprovide fuel injection, but also to provide a motivating source forengine braking operation. One advantage of using the high pressure fluidsource, such as source 100, for engine braking is that it is alreadyresident in the engine. In order to take advantage of the high pressuresource 100 for engine braking purposes, pressurized fluid from the highpressure fluid source 100 may be provided through a high pressure line140 to a pressure reducing device 300. The pressure reducing device 300preferably may reduce the pressure of the fluid by approximately amagnitude, and more preferably to a level of approximately 300 psi. Thereduced pressure fluid may be provided through line 310 to a controlvalve 400. The pressure provided by the pressure reducing device 300 maybe indicated by pressure P2.

[0027] In one embodiment, the pressure reducing device 300 may comprisea pressure reducing valve. The pressure reducing device 300 may comprisea directly-operated pressure reducing valve, a two-way pilot-operatedpressure reducing valve, and/or any other known pressure reducing valve.As will be apparent to those of ordinary skill in the art, otherpressure reducing devices adapted to reduce the pressure of the fluidfrom the high pressure fluid source 100 are considered to be within thescope and spirit of the present invention.

[0028] With continued reference to FIG. 3, the control valve 400 mayinclude a valve body 410 and a controller 420. The valve body 410 ispreferably a 3/2 directional control valve and may include internalpassages that connect a first port 412 with a second port 414, and athird port 416 with a fourth port 418. The valve body 410 may be biasedinto a default position by a control valve spring 430.

[0029] In the default position the internal passages in the valve body410 may connect the brake actuator line 440 with an accumulator 500. Inan alternative embodiment, as shown in FIG. 4, the accumulator 500 maybe replaced with a vent or a fluid return line that connects the controlvalve 400 to the low pressure tank 200.

[0030] The controller 420 may be used to translate the valve body 410 sothat fluid flows to and from the brake actuator line 440. In FIG. 3, thevalve body 410 may be translated linearly toward the control valvespring 430. The controller 420 may be any suitable device fortranslating the valve body 410 at high speed. It is appreciated that thecontroller 420 may be a hydraulic, hydroelectric, mechanical,piezoelectric, or electromagnetic (e.g. solenoid) device. The controller420 preferably is capable of translating the valve body 410 at leastonce, and preferably more than once per engine cycle.

[0031] It is further appreciated that the controller 420 is preferablycontrolled by an electrical signal issued by an engine control module(ECM) (not shown). As will be apparent to those of ordinary skill in theart, the ECM may include a microprocessor, and may be connected tosensors linked to other engine components, such as for example, theengine cylinder, the exhaust manifold, the intake manifold, or any otherengine component, to control the controller 420.

[0032] The brake actuator line 440 provides fluid communication betweenthe control valve 400 and the engine valve actuator 600. The enginevalve actuator 600 includes a fluid chamber 610, an actuator piston 620disposed to slide in the fluid chamber, and a return spring 630.

[0033] The return spring 630 is shown inside of the fluid chamber 610,however, it is appreciated that the return spring may be provided at anylocation between the engine valve actuator 600 and the engine cylinder(not shown). The return spring 630 may even be provided as a returnspring for the dedicated brake valve 700 since return of the dedicatedbrake valve 700 to its up most position will also return the actuatorpiston 620 to its up most position.

[0034] The actuator piston 620 may terminate in an engine valve head, oralternatively, actuate an engine valve 700 dedicated to the brakingand/or exhaust gas recirculation function. The engine valve 700 providesselective communication between an engine cylinder 720 and an exhaustmanifold 710. The return spring 630 may bias the actuator piston 620toward the upper end of the fluid chamber 610. In this position thededicated engine valve 700 is closed.

[0035] The control valve 400 may assume two primary positions under theinfluence of the controller 420. A first position of the control valve400 corresponds to the condition in which no engine braking and/orexhaust gas recirculation is desired, i.e. the dedicated engine valve700 is closed. When the dedicated engine valve 700 is to be closed, thecontroller 420 maintains the valve body 410 in the position shown inFIG. 3. In this position the first port 412 of the valve body 410communicates with the brake actuator line 440 and the second port 414communicates with the accumulator 500. As a result, the valve body 410provides communication between the fluid chamber 610 and the accumulator500. Fluid pressure in the accumulator 500 is low, and, accordingly, thededicated engine valve return spring (which may be spring 630) candisplace the actuator piston 620 upward to push fluid out of the fluidchamber 610 and into the accumulator 500. No new fluid may flow into thefluid chamber 610 to displace the actuator piston 620 downward becausethe control valve 400 is not in a position in which it providescommunication between the reduced pressure line 310 and the brakeactuator line 440.

[0036] When engine braking and/or exhaust gas recirculation is desired,the actuator piston 620 may be displaced downward to actuate thededicated engine valve 700 as a result of application of reducedpressure fluid from the control valve 400 on the actuator piston. Whenthe actuator piston 620 is displaced downward toward the dedicatedengine valve 700, the dedicated engine valve is open and gas is free toflow between the engine cylinder associated with the dedicated enginevalve and the exhaust manifold.

[0037] As an initial matter, the system may be turned “on” for braking,EGR, or other valve actuation duty by applying reduced fluid pressurefrom the pressure reducing device 300 to the reduced pressure line 310.Once fluid pressure exists in the reduced pressure line 310, thecontroller 420 may be instructed to translate the valve body 410downward. This downward translation causes the third port 416 of thevalve body to align with the reduced pressure line 310, and the fourthport 418 to align with the brake actuator line 440. In this position thevalve body 410 provides fluid communication between the reduced pressureline 310 and the brake actuator line 440. This communication causes thebrake actuator piston 620 to translate downward and open the enginevalve 700 for an engine braking or exhaust gas recirculation event.

[0038] The foregoing cycle of opening and closing the engine valve 700may be carried out as quickly as the controller 420 can cause the fluidchamber 610 to drain and refill. It is apparent that the speed of thesystem will depend upon the speed and size of the control valve 400, thesize and length of the brake actuator line 440 and the viscosity of theworking fluid. Accordingly, it may be advantageous to locate the controlvalve 400 as close as possible to the fluid chamber 610 to improve theresponse time of the system. For some embodiments of the invention, Itis desired that the system be capable of more than one engine valveevent per engine cycle, and that the system provide an almost infinitevariety of timing selections for the opening, closing, and duration ofbraking and EGR events. Although it is desirable for the system to becapable of high speed actuation, the system need not always be operatedat a high speed to provide beneficial results. For example, the system10 could be used to provide partial or full cycle bleeder braking duringtimes that braking noise is a concern (in a town or city), and toprovide compression release type braking at other times when noise is ofless concern.

[0039] The use of a reduced fluid pressure (i.e., on the order of 300psi as opposed to 3000 psi) for the actuation of the dedicated enginebraking valve 700 may provide several advantages. Advantages realizedduring braking and/or EGR include the fact that a high-speed triggervalve used as control valve 400 may be easier to make and more reliablebecause it need only handle reduced pressure fluid. The use of reducedpressure fluid may also reduce the impact load and seating velocity ofthe braking components and make such loads and velocities morecontrollable. Furthermore, the use of reduced pressure fluid may reducefluid leakage and vibration of the braking system, and make the overallsystem more compact. Advantages realized during positive power includenear infinite variation of valve timing to provide internal EGR tailoredto engine speed and/or load. The system 10 could also be modified toprovide cooled internal EGR since the exit passage for the dedicatedvalve can be different from that for the main exhaust valves and acooler can be provided in the dedicated passage.

[0040] An alternative embodiment of the present invention is shown inFIG. 5, in which like reference numerals refer to like elements. In thesystem shown in FIG. 5, the engine valve actuator 600 is provided by anelectromagnetic actuator 690. In this embodiment, there is no need for acommon rail system, as in the system of FIG. 3. In all other respects,the system of FIG. 5 may be operated similarly to the system shown inFIG. 3.

[0041] In one embodiment, the electromagnetic actuator 690 may comprisea high-speed solenoid valve capable of actuating the engine valve 700 ata rate of at least once per engine cycle. In another embodiment, theelectromagnetic actuator 690 may comprise a low-speed solenoid valve.Other embodiments of the engine valve actuator 600, including, but notlimited to, a piezoelectric actuator are considered within the scope andspirit of the present invention.

[0042] The dedicated engine valve 700 for engine braking and EGR may besmaller than the main exhaust valve and may need less force to open it.Once the valve is fully open, the flow area through the valve iscontrolled by the annular gap between the bore and the valve stem, andeven less force may be needed to keep the valve open.

[0043] It will be apparent to those skilled in the art that variationsand modifications of the present invention can be made without departingfrom the scope or spirit of the invention. For example, the relativepressures of the high pressure system and the reduced pressure systemmay be different from those referenced in the foregoing discussionwithout departing from the intended scope of the invention. The size anddesign of the individual components may vary, and some components, suchas the accumulator, the pressure sensors, etc., may be eliminatedwithout departing from the intended scope of the invention. Further,design of the control valve 400 may vary without departing from theintended scope of the invention. Furthermore, the hydraulic fluid usedcan vary without departing from the intended scope of the invention. Inaddition, embodiments of the methods and apparatus of the presentinvention may be adapted for two-stroke engine braking, in which thenormal engine exhaust and intake valve events are modified, as well asfour-stroke engine braking. Thus, it is intended that the presentinvention cover all such modifications and variations of the invention,provided they come within the scope of the appended claims and theirequivalents.

What is claimed is:
 1. An engine valve actuation system, comprising: ahigh pressure hydraulic fluid passage; a high pressure hydraulic fluidsource; a fluid pressure reduction device connected to the hydraulicfluid source through the high pressure hydraulic fluid passage; a lowpressure hydraulic fluid passage; a hydraulic fluid control valveconnected to the fluid pressure reduction device through the lowpressure hydraulic fluid passage; an actuator hydraulic fluid passage;and an engine valve actuator for actuating an engine valve to produce anengine valve event, the engine valve actuator communicating with thehydraulic fluid control valve through the actuator hydraulic fluidpassage.
 2. The system of claim 1, wherein the engine valve event isselected from the group consisting of: a compression release brakingevent, a bleeder braking event, and an exhaust gas recirculation event.3. The system of claim 1, wherein the hydraulic fluid source comprises afuel injection system.
 4. The system of claim 1, wherein the fluidpressure reduction device reduces the pressure of the hydraulic fluidfrom a first pressure to a second pressure having a pressure ofapproximately a magnitude lower than the first pressure.
 5. The systemof claim 4, wherein the second pressure is approximately 300 psi.
 6. Thesystem of claim 1, wherein the control valve comprises: a valve bodyhaving a plurality of fluid passages formed therein, the valve bodyadapted to selectively translate between a first operating position anda second operating position; a controller for translating the valvebody; and a spring for biasing the valve body into the first operatingposition.
 7. The system of claim 6, wherein the controller translatesthe valve body at a rate of at least once per engine cycle.
 8. Thesystem of claim 6, further comprising an accumulator, wherein thecontrol valve connects the actuator hydraulic fluid passage with theaccumulator when the valve body is in the first operating position. 9.The system of claim 6, wherein the control valve connects the actuatorhydraulic fluid passage with a low pressure hydraulic fluid tank whenthe valve body is in the first operating position.
 10. The system ofclaim 6, wherein the control valve connects the actuator hydraulic fluidpassage with the low pressure hydraulic fluid passage when the valvebody is in the second operating position.
 11. The system of claim 1,wherein the engine valve actuator comprises: a fluid chamber forreceiving hydraulic fluid from the actuator hydraulic fluid passage; anactuator piston slidably disposed in the fluid chamber; and a returnspring in contact with the actuator piston.
 12. The system of claim 1,further comprising: a low pressure hydraulic fluid tank, and wherein thehydraulic fluid source further comprises: a high pressure pump incommunication with the low pressure fluid tank; a pressure regulator;and a high pressure plenum connected to the high pressure hydraulicfluid passage.
 13. The system of claim 1, wherein the engine valve is adedicated engine exhaust valve.
 14. The system of claim 1, wherein theengine valve requires less force to actuate it than a main exhaustvalve.
 15. An engine valve actuation system, comprising: a high pressurehydraulic fluid source for providing hydraulic fluid at a firstpressure; a fluid pressure reduction device connected to the hydraulicfluid source; a hydraulic fluid control valve connected to the fluidpressure reduction device having a first operating position and a secondoperating position; and an engine valve actuator for actuating an enginevalve to produce an engine valve event adapted to receive the hydraulicfluid at a second pressure when the hydraulic fluid control valve is inthe second operating position.
 16. The system of claim 15, wherein thesecond pressure is approximately 300 psi.
 17. A method of actuating anengine valve in an internal combustion engine to produce an engine valveevent, the method comprising the steps of: providing hydraulic fluid toa fluid pressure reduction device; reducing the pressure of thehydraulic fluid from a first pressure to a second pressure; selectivelyapplying the hydraulic fluid at the second pressure to an engine valveactuator; and actuating the engine valve to produce the engine valveevent.
 18. The method of claim 17, wherein the step of actuating theengine valve further comprises the step of producing a compressionrelease braking event.
 19. The method of claim 17, wherein the step ofactuating the engine valve further comprises the step of producing ableeder braking event.
 20. The method of claim 17, wherein the step ofactuating the engine valve further comprises the step of producing anexhaust gas recirculation event.